A criminal justice system that is empowered, highly trained, well-resourced, and efficient can be used to repress the common people with violence as well as protect them from violence. Moreover, such systems are the coercive arm of the state (controlled by a ruling regime); while governments may be very happy to have outsiders come and tinker with their hospitals, schools, and farming techniques, they are much more reluctant to have outsiders mess around with their systems of justice, policing, and legal accountability.
